Axial Thrust Force Research Articles

Effects of secondary injection on the performance of over-expanded single expansion ramp nozzle

Scramjets with Single expansion ramp nozzle (SERN) is one of the most promising candidates for an airframe integrated hypersonic vehicle propulsion system. So, studying the performance of the SERN at various flight conditions is very important to improve the overall performance of the propulsion system. The main problem with a SERN is, it tends to exhibit poor performance characteristics at the over-expanded or off-design operating conditions. So, to improve the performance of the SERN at off-design conditions, the present numerical study focuses on using various secondary injection techniques on the cowl and ramp surfaces. The freestream Mach number considered for the current study is 3, and the corresponding nozzle pressure ratio (NPR) for the SERN is 20. The effects of injection pressure, location, and angle on the axial thrust force and normal force are parametrically studied. It is found that the introduction of secondary injection significantly affects the pressure distribution over the cowl and ramp surface. This change in pressure distribution directly reflects on the magnitude of the normal force and axial thrust force generated by the SERN. The secondary injection also influences the shock pattern of the main nozzle flow.

Investigation of the Axial Rotor Thrust in Centrifugal Compressors استقصاء الدفع المحورى على العضور الدوار فى الضواغط النابذة

الهدف من البحث هو دراسة وتحليل والتعين الدقيق للدفع المحورى علىالعضو الدوار فى الضواغط الطاردة المرکزية. نشرح العوامل التى تؤثر علىالدفع المحورى مثل زيادة الأحمال على ضاغط ثانى أکسيد الکربون عنأوضاع التشغيل التصميمية له . کما تتضمن العوامل تأثير وجود Fouling مع الغاز مما ينتج عنه تراکم على الأسطح الداخلية لدفاعات العضو الدوارفيتسبب فى زيادة الدفع المحورى وتقليل من أداء الضاغط . يتناول البحثشرح العلاقة مابين الدفع المحورى للعضو الدوارفى وجود نسبة Foulingمع الغاز فى خلال فترة زمنية محددة من بعد عمل عمرة کاملة لضاغط ثانىأکسيد الکربون . بعد الدراسة والتحليل نقف على کيفية تقليل الدفع المحورىعلى العضو الدوار وذلک بوضع اسطوانة اتزان على العضور الدوار لخلققوى معاکسة له تتناسب مع جميع الظروف التشغيلية لضاغط ثانى أکسيدالکربون بحيث أن الدفع المحورى للعضو الدوار بعدها لا يتعدى 50 % منحمل الکرسى. النتائج النهائية التى تم الحصول عليها: عند استخدام قطراسطوانة اتزان = 158.6686 mmt D تکون أعلى قيمة للدفع المحورى عنأوضاع التشغيل المختلفة للضاغط هى 93.193 % من حمل الکرسى. عنداستخدام قطر اسطوانة اتزان = 186.065 mmt D تکون أعلى قيمة للدفعالمحورى عن أوضاع التشغيل المختلفة للضاغط هى 73.35 % من حملالکرسى. عند استخدام قطر اسطوانة اتزان = 174.595 mmt D تکونأعلى قيمة للدفع المحورى عن أوضاع التشغيل المختلفة للضاغط هى41.22 % من حمل الکرسى مع وجود Fouling مع الغاز وعند أقصى حملللضاغط بعد العمرة فى عدم وجود Fouling مع الغازهى 0 % من حملالکرسى وهذا يعتبرأنسب قطر يستخدم لاسطوانة الاتزان (Balance drum)لان الدفع المحورى يکون أقل من % 50 من حمل الکرسى.Abstract: This article is a study, analysis, and determine accurately the axial rotor thrust for centrifugal compressors. Are explained the factors that affect axial rotor for carbon dioxide compressor during operating conditions. Also, the effect of the existence of fouling with gas, results in the accumulation of fouling on the internal surfaces of the impellers leading to an increase in axial rotor thrust and reduction of the performance of the compressor. The relationship between axial rotor thrust and fouling ratio with time is discussed after complete overhaul for the carbon dioxide compressor. The axial rotor thrust on the carbon dioxide compressor is reduced by placing balance drum on rotor of the compressor in the opposite direction of the axial force which is suitable for all operating conditions of the compressor. The resultant axial force didn’t exceed 50 % of rated bearing load, and the analysis method is then approved to be effective. The residual thrust load for high pressure rotor for the compressor before modification at design operating condition is equal to 13.68 % of rated bearing load, while at the high load without fouling effect for the compressor is equal to 58.47 % of rated bearing load and compressor with fouling effect is equal to 110.9 % of rated bearing load. When using the balance drum diameter Dt =158.6686 mm, the highest value of axial thrust force is equal to 93.193 % of rated bearing load. When using the balance drum diameter Dt =174.595 mm, the highest value of axial thrust force is equal to 41.22 % of rated bearing load. When using the balance drum diameter Dt =186.065 mm, the highest value of axial thrust force is equal to 73.35 % of rated bearing load.

CFD based evaluation of conventional electrical submersible pump for high-speed application

Fluctuations in oil prices have negatively affected the petroleum industry, prompting to look for innovative ways to optimize oil recovery. One of the current approaches to optimize oil production is to employ high-speed ESPs with Permanent Magnet Motors (PMM) that allow reducing the pump size while increasing the operating envelop. Standard affinity laws are a useful tool to provide a preliminary estimate of common pump performance. However, there is a need to understand the detailed variation in the flow variables and losses incurring due to fluid-geometry interactions at high rotational speeds. To evaluate the hydraulic performance of a mixed flow pump, Computational Fluid Dynamics (CFD) simulations were performed at rotational speeds ranging from 3600 rpm to 20000 rpm using fluids with different viscosities. Fluid behavior is studied by observing the change in flow parameters with rotational speed. Similitude analysis is utilized to characterize the pump performance. The numerical results yielded improved pump hydraulic performance with an increase in rotational speeds which is attributed to reduced separation losses mainly in the diffuser section. Research is concluded with further evaluation of the complete stage including secondary leakage flow path on flow variables and axial thrust forces.

Experimental evaluation of cortical bone substitute materials for tool development, surgical training and drill bit wear investigations

Surgeons, scientists and development engineers of surgical devices require phantoms and materials for testing and training purposes. Human or animal bones are the gold standard, but difficult to obtain, prepare and handle. While polyurethane foams can be used as a substitute for trabecular bone, cortical bone substitutes have not been evaluated. In this study, a standard surgical drill bit (⌀ 3.2 mm) with clinical process parameters was used to compare 5 different materials with bovine cortical bone: polyurethane with three different densities, short-fiber-filled epoxy and an artificial bone material. Drillings were repeated 100 times with 6 drill bits for each material. The results indicate that none of the substitute materials can be used without compromises. Axial drilling thrust forces in short-fiber-filled-epoxy are similar to bone. However, its hard fibers significantly deteriorate the chisel edge and flank face and increases the thrust force with each drilling (doubles within the first 10 repetitions) so that drill bits should only be used very limited times. The densest polyurethane (Renshape BM-5166) has the advantage of comparable torque values with bovine cortical bone (up to 60 repetitions). Additionally to these findings, a significant and potentially clinical relevant increase of axial drilling force (80%) and torque (56%) was found during 100 drillings in bovine cortical bone.

Unsteady RANS simulation of three-stage centrifugal pumps with different impeller-diffuser gaps

In this study, unsteady RANS simulation is attempted for a three-stage centrifugal pump, a target pump for the workshop “Single- & Multi-Stage Pump Flow Prediction” which is being held in 29th IAHR Symposium on Hydraulic Machinery and Systems. A commercial code SCRYU/Tetra developed by Software Cradle Co. Ltd. is adopted for the unsteady RANS simulation. Our primary interest is to understand the effect of the gap between impeller trailing edge and diffuser leading edge on the axial thrust characteristics of the multi-stage centrifugal pumps. To do so, in addition to the simulation for the original pump model, the impeller-diameter cut model is also simulated. The diffuser inlet to the impeller outlet diameter ratio is 1.05 for the cut model against 1.02 for the original model. The good agreement is obtained for the hydraulic performance of the original model at the design flow rate, but only the fair agreement is obtained for the axial thrust force. From the pressure distributions inside the front and back side gap of the impeller, it is found that the discrepancy is due to that of the pressure distribution inside the back side gap of the second (and also perhaps the first) impeller. The effect of impeller-diffuser gap on the hydraulic performance and axial thrust force is predicted to be small at the design flow rate through the present computations. At the low flow rate, the balancing flow rate is significantly over-predicted by the present simulation. The reason for this remains unclear and will be hopefully made clear in our future study.

An experimental study on interference friction welding process

Interference friction welding process is a variant of friction welding processes that has been proposed to be used to join a tube/round bar to a sheet metal/plate. The rotating tube is made to pass through the punched or drilled hole of smaller diameter and hence the interference causes the plastic deformation and frictional heat due to sliding contact in axial direction (due to tube feed) and tangential direction (due to tube rotation). In this investigation, the effect of different process parameters such as feed rate, spindle speed, amount of interference, and penetration depth of the tube on the axial thrust force and the torque generated at the weld interface has been studied. The change in torque and thrust force values were related to the amount of heat generation and plastic deformation at the interface that contributes to the quality of the solid state weld joint being formed. The quality of the weld joints formed at different parameters were evaluated from the microscopic analysis and shear testing. Moreover, the joint strengths were compared with the interference fit joints that were formed from the shrink fitting operation. It has been observed that, with appropriate process parameters, interference friction welding process can be performed on a typical machine tool, and it is feasible to create a weld with good joint strength.

Operational performance analysis of spiral capsule robot in multiphase fluid

SUMMARYMinimally invasive surgery is a developing direction of modern medicine. With the successful development of controllable capsule endoscopies, capsule robots are very popular in the field of gastrointestinal medicine. At present, the study of intestinal robots is aimed at the pipeline environment of a single-phase liquid flow. But there exist food residues (i.e. solid particles) or liquid foods in the actual intestine, so intestinal fluid should be liquid–solid or liquid–liquid two-phase mixed fluid. For inner spiral capsule robots with different internal diameters and outer spiral capsule robots, using computational fluid dynamics (CFD) method, the operational performance indicators (i.e. axial thrust force, circumferential resisting moment and maximum pressure to pipeline wall) of spiral capsule robots are numerically calculated in the liquid–solid or liquid–liquid two-phase mixed fluid. By the orthogonal experimental optimization method, the optimum design of spiral capsule robots is obtained in the liquid–solid mixed fluid. The experimental verification has been also carried out. The results show that in the liquid–solid two-phase fluid, the axial thrust force and circumferential resisting moment of the spiral capsule robots decrease with the increase of the size or concentration of solid particles. In the same liquid–solid or liquid–liquid mixed fluid, the operational performance indicators of outer spiral robots are much higher than those of inner spiral robots, and the operational performance indicators of inner spiral robots with bigger internal diameters are higher than those with smaller internal diameters. Adding solid particles of high concentration in the pipeline containing liquid will reduce the drive performance of spiral capsule robots, but adding another liquid of high viscosity will improve the drive performance of spiral capsule robots.

Design and manufacture of new type of non-circular cylindrical gear generated by face-milling method

Face-milling cutting method, widely used in the generation of spiral bevel gear, can also be applied to cylindrical gear fabrication. This paper, generalizing the method to non-circular gear fabrication, proposes a new curvilinear non-circular cylindrical gear type.Compared to spur non-circular gear, this new gear type has a higher contact ratio and compared to helix non-circular gear, it has a smaller axial thrust force. Besides, demonstrating a localized contact pattern, the gear is insensitive to processing and alignment errors. Furthermore, during the driving process, the gear can retain oil within the concave tooth surface, bringing better lubrication.Based on the face-milling cutting method and non-circular gear meshing theory, this paper investigates into curvilinear non-circular gear generation, including the mathematical model for design and the linkage model for manufacture.

The effects of blade twist and nacelle shape on the performance of horizontal axis tidal current turbines

The paper presents the effects of blade twist and nacelle shape on the performance of horizontal axis tidal current turbines using both analytical and numerical methods. Firstly, in the hydrodynamic design procedure, the optimal profiles of untwisted and twisted blades and their predicted theoretical turbine performance are obtained using the genetic algorithm method. Although both blade profiles produce desired rated rotational speed, the twisted blade achieves higher power and thrust performance. Secondly, numerical simulation is performed using sliding mesh technique to mimic rotating turbine in ANSYS FLUENT to validate the analytical results. The Reynolds-Averaged Navier-Stokes (RANS) approximation of the turbulence parameters is applied to obtain the flow field around the turbine. It is found that power and axial thrust force from BEMT (Blade Element Momentum Theory) method are under-predicted by 2% and 8% respectively, compared with numerical results. Afterwards, the downstream wake field of the turbine is investigated with two different nacelle shapes. It is found that the rotor performance is not significantly affected by the different nacelle shapes. However, the structural turbulence caused by the conventional nacelle is stronger than that by the NACA-profiled shape, and the former can cause detrimental effect on the performance of the downstream turbines in tidal farms.

立軸斜流ポンプの吸込み水槽渦による軸スラスト挙動

Axial thrust forces acting on an impeller of a diffuser type mixed flow pump and the behavior of the axial thrust generated by the vortex occurrence in a pump intake sump were studied. The thrust from distinct discontinuities, such as the hysteresis phenomenon, was measured from a pump's hydraulic performance. In pump partial load operation the axial thrust increases discontinuously because of the reverse flow at impeller inlet. Synchronous and non-synchronous components of axial thrust increase during the onset of reverse flow zones. A prediction method for static axial thrust was derived based on Oshima's theory, accounting for the pressure reduction at pump suction bell-mouth caused by a vortex. Qualitative comparison of the predicted results with the actual static axial thrust results measured during the experiment, showed reasonable similarities around pump best efficiency flow rate. The thrust was measured using a pump intake sump test apparatus in which both an air-entrained surface vortex and a submerged vortex could occur. The level of dynamic axial thrust is dependent on the pump intake sump water level and the dynamic axial thrust begins to increase when a full air core vortex occurs at the pump intake. When submerged as well as full air core continuous vortices occur, the axial thrust and the fluctuation of total pump head become abruptly large. The fluctuation of axial thrust becomes the highest when the impeller draws in a large air-drawing vortex, imposing a pressure fluctuation which generates not only a rotational speed but also nZ vane passing and low frequency components.

Non-Contact DC Electromagnetic Propulsion by Multipole Transversal Field: Numerical and Experimental Validation

This paper describes the numerical and experimental validation of a novel non-contact dc electromagnetic propulsion concept. In the proposed approach, a propulsion coil carrying a dc current is surrounded by a dc transversal multipole field created inside of a launch tube. The interaction between the transversal dc magnetic field and a dc propulsion coil results in the generation of axial (thrust) force with no need of sliding contacts. This paper describes a numerical assessment of the field-current-force interactions based on both analytical calculations and finite elements, and the corresponding validation experiments. The experiments demonstrate the generation of contactless axial (thrust) force in a dc launch coil using a dc transversal multipole field, and provide a benchmark for the model-based prediction of the field-current-force interactions. Partial magnetic shielding of the propulsion coil is used to selectively attenuate the magnetic field experienced by the thrust coil in a way that a net thrust force is achieved. Experimental measurements confirmed that it is indeed possible to generate contact-free thrust force on a dc propulsion coil using a dc multipole magnetic field, and the measured values of thrust force are in good agreement with the corresponding predictions.

Model test investigation of a spar floating wind turbine

Several floating wind turbine designs whose hull designs reflect those used in offshore petroleum industry have emerged as leading candidates for the future development of offshore wind farms. This article presents the research findings from a model basin test program that investigated the dynamic response of a 1:50 scale model OC3 spar floating wind turbine concept designed for a water depth of 200 m. In this study the rotor was allowed to rotate freely with the wind speed and this approach eliminated some of the undesirable effects of controlling wind turbine rotational speed that were observed in earlier studies. The quality of the wind field developed by an array of fans was investigated as to its uniformity and turbulence intensity. Additional calibration tests were performed to characterize various components that included establishing the baseline wind turbine tower frequencies, stiffness of the delta type mooring system and free decay response behaviour. The assembled system was then studied under a sequence of wind and irregular wave scenarios to reveal the nature of the coupled response behaviour. The wind loads were found to have an obvious influence on the surge, heave and pitch behaviour of the spar wind turbine system. It was observed from the experimental measurements that bending moment at the top of the support tower is dominated by the 1P oscillation component and somewhat influenced by the incoming wave. Further it was determined that the axial rotor thrust and tower-top shear force have similar dynamic characteristics both dominated by tower’s first mode of vibration under wind-only condition while dominated by the incident wave field when experiencing wind-wave loading. The tensions measured in the mooring lines resulting from either wave or wind-wave excitations were influenced by the surge/pitch and heave couplings and the wind loads were found to have a clear influence on the dynamic responses of the mooring system.

Active bearing force reduction in non-commutated linear actuators

Planar linear magnetic actuators are used in a wide range of industrial applications. Permanent magnet movers in particular allow high axial thrust forces, which result in considerable destabilizing stiffness in the direction perpendicular to the direction of motion. These forces, which can reduce bearing lifetime significantly, must therefore be stabilized with linear bearings. This paper introduces an integrated active bearing-force compensation concept that minimizes the forces acting on the mechanical bearings. The potential and limits of bearing force compensation are analyzed based on a short-stroke linear actuator with an E-shaped stator. Further, the extent to which bearing forces can be compensated for, even with simple actuator layouts, is described. Particularly in linear oscillating drives, such compensation can (i) significantly reduce wear and thus improve lifetime and (ii) reduce the size of mechanical bearings. Measurements of a prototype system confirm the simulated results.

立軸斜流ポンプ羽根車に働く軸スラストの挙動

Axial thrust forces acting on an impeller of a diffuser type mixed flow pump have been studied. The behavior of the axial thrust generated by the vortex occurrence in a pump intake sump was investigated. The thrust of distinct discontinuities such as hysteresis phenomenon from a pump hydraulic performance was measured. In pump partial load operation the axial thrust increases discontinuously because of the reverse flow at impeller inlet. Synchronous and non-synchronous components of axial thrust increase during the onset of reverse flow zones. A prediction method for static axial thrust was derived based on Oshima's theory accounting for the pump suction bell-mouth pressure reduction due to vortex. Qualitative comparison with the measured experimental results for static axial thrust showed reasonable agreement around pump best efficiency flow rate. The pump intake sump test apparatus，in which both an air-entrained surface vortex and a submerged vortex will occur，was employed and the axial thrust was measured. The level of axial thrust is dependent on the pump intake sump water level. The dynamic axial thrust begins to increase due to the occurrence of a full air core vortex to intake. When submerged as well as full air core continuous vortices occur，the axial thrust and the fluctuation of total pump head become abruptly large. The fluctuation of axial thrust becomes the highest when the impeller sucks the air-drawing large vortex imposing a pressure fluctuation which generates not only a rotational speed but also nZ vane passing and low frequency components.

An analytical and experimental study for predicting the axial thrust forces in a turbocharger

An analytical and experimental study for predicting the axial thrust forces in a turbocharger

Operational numerical simulation of a four-spiral in-pipe robot

Based on an in-pipe robot with four spiral bodies in its tail, the dynamics equations of the fluid in the pipe are established when the robot runs. By using the computational fluid dynamics (CFD) method, the robot’s force, circumferential torque and pressure on the pipe are numerically analyzed when the spiral directions of four spiral bodies are alternately left-handed and right-handed or are all left-handed, and different spiral directions correspond to different rotational directions. When the robot is needed to change direction, the rotational directional combinations of the four spiral bodies are calculated and designed. The results show that when the spiral directions of four spiral bodies alternate and the rotational directions of spiral bodies with different spiral directions are different, the formed axial thrust forces are the same, and the formed radial forces are counterbalanced, so that the robot moves axially in a balanced state. When the spiral and rotational directions of four spiral bodies are the same, the uniform axial thrust forces and a certain circumferential torque are formed, so that the robot moves axially in a rotating state. Under the two conditions, the robots can achieve turning arbitrarily. The turning directions of the four-spiral robots only relate to the rotational directions of the robotic spiral bodies. By contrasting the numerical values and the experimental values of the thrust forces between the cylinder and the spiral ribbed plate in the reference, the correctness of the numerical calculation method used in this paper is verified. The above research shows that such multi-spiral in-pipe robots are suitable to achieve inspection, dredging and other functions.

Towards a Novel, Implantable Limb Lengthening Device1

Several surgical techniques and devices have been developed to help patients born with limb deformities, limb length inequalities, and extreme short stature. People with such ailments often experience pain, dysfunction, and joint degeneration. The primary method of treating such deformities is an osteotomy followed by callus distraction [1]. Commonplace lengthening devices are external fixators and intramedullary devices, but each has its drawbacks. Traditional external fixators, such as the Ilizarov device and Taylor spatial frame, are cumbersome, painful, and produce large residual scars [2]. Due to pin tract infection rates of 10–20%, lengthening with these methods requires careful surveillance [3]. Intramedullary lengthening devices can cause severe complications such as intramedullary infection [4]. Surgeons have recently experienced success with a motorized, intramedullary nail (Fitbone), but pediatric use of this device can be limited due to interference with open growth plates [5]. The investigators have designed an extramedullary device that retains the attractive qualities of an intramedullary nail, without the risk of deep infection or damage to growth plates. Additionally, the device can be equipped with a six-axis force-torque sensor capable of measuring forces and moments in real time.

Modelling, analysis and experiments of a screw propelling capsule robot

Active locomotion has been a challenge in the research and development of capsule endoscopies for diagnosis and therapy inside gastrointestinal tracts. As one prospective solution to the active locomotion of capsule robots, screw propelling has many important issues to be addressed in both theory and practice. In this paper, we build one- and two-dimensional models of screw propelling and make quantitative analysis to find the relationship between the axial thrust force and the geometric parameters of the screws, for optimal design of the actuation mechanism with high efficiency of propulsion. A few prototypes of the capsule robots are developed and a series of contrast experiments are conducted to verify the theoretical models and analysis. The effectiveness of active drive of capsule robots by screw propelling has been preliminarily shown by the experiments with the prototypes crawling in a tube.

A Study of the Stability for Axial Thrust Force Vibration in Balancing Piston Mechanism

A Study of the Stability for Axial Thrust Force Vibration in Balancing Piston Mechanism

Fire Performance of Corrosion-Damaged Reinforced Concrete Beams

This experimental study examines the effects of fire on corrosion-damaged reinforced concrete beams. Nine beams were cast with the same external dimensions and amount of reinforcement. Corrosion was induced in the beams by a constant current source. The beams were tested at constant service load while being exposed to the CAN/ULC-S101 time-temperature curve. The results indicated that the deflection of reinforced concrete beams increased during a fire exposure as the level of corrosion damage increased. The corrosion products within the pores of the concrete provided a limited insulating effect on the heat front penetration through the concrete cover. Temperature differential developed at the steel level was shown to help delay failure of the beams by the development of the axial thrust force. A major factor affecting the performance of corrosion damaged beams during a fire exposure was the ability of the concrete cover to remain in place.